The fraction of original whisky in a whisky-water mixture is distinct from the mixture's ethanol fraction; final ABV also depends on starting ABV and the volume model.
Definition And Application
For a nominal additive-volume mixture, whisky fraction = whisky volume / (whisky volume + water volume). Estimated final ABV = starting ABV × whisky fraction. These are different quantities even when both are expressed as percentages.
For example, 30 mL of 40% ABV whisky plus 10 mL water gives a whisky fraction of 75% and estimated final ABV of 30%. The calculation is a planning model, not certified measurement.
Ashmore's dilution treatments and Smith's inconsistent preparation description illustrate why the definitions matter. Smith's stated approximately 23% ABV cannot be recovered from the reported 30:10 volumes and starting strengths; do not silently assume actual preparation.
Whisky dilution changes both headspace chemistry and discrimination — Ashmore et al.- The Perceptual Categorisation of Blended and Single Malt Scotch Whiskies — Evidence and Blending Lab Applications
- Whisky: Technology, Production and Marketing — Evidence and Blending Lab Applications
The established definition does not predict aroma, preference or an optimal drinking strength.